Forensic Science Overview and Court Systems

Forensic Science Overview

• Forensic Science: Science used in a court of law/justice system
• Criminalistics: Science of individualization; analyzes and interprets crime scene evidence, reconstructs the crime
• CSI Effect: Public perception of unrealistic standards in the legal system due to TV portrayals
• Penny Parker Case: Solved using DNA profiling; partial DNA match to suspect's daughter, ultimately confirmed by suspect's sample

Court Systems

• Civil Court: Aims to assign fault and determine compensation for civil disputes (approx. likelihood of placing fault: 50%)
• Criminal Court: Deals with law violations, resulting in citations or arrests; defendants face felony or misdemeanor charges

Expert Witness Qualifications

• Demonstrates knowledge of methods and limitations
• Familiar with scientific literature
• Clearly presents the basis of their opinions
• Testifies independently about scientific results
• Accepts scrutiny by opposing counsel (judge's decision)

Crime Lab Careers

• DNA Analyst: Analyzes biological samples (blood, bone, hair, saliva, semen) using databases and statistical analysis.
• Toxicologist: Analyzes blood, urine, and tissue for drugs, narcotics, and alcohol.
• Trace Analyst: Examines paint, hair, fibers, soils, ropes, tape, and explosive residue.
• Firearms Analyst: Analyzes bullets and cartridge cases to determine their origin and reconstruct shootings.

Educational Requirements

• Bachelor's degree in a science is a standard requirement for a crime lab career

Crime Lab Challenges

• Maintaining a consistent standard of evidence handling and evaluation among different labs.
• DNA Analyst: Likely needs more biology- and lab-focused courses.

Solving Crime: Fundamentals

• Forensic Science: Using science to resolve legal disputes
• Criminalistics: Science of individualism
• Locard Exchange Principle: Every contact leaves a trace
• Forensic Diamond: Framework for connecting victim, suspect, crime scene, and evidence
• Evidence Types: Include animal hair, building materials, chemical analysis, powder, liquids, and stains.

Death and Crime Scene Investigation

• Manner of Death: How death occurred (suicide, homicide, natural, accidental, undetermined)
• Cause of Death: The specific injury or disease that caused death (e.g., gunshot wound, heart attack)
• Rigor Mortis: Muscle stiffening after death; timeline is useful.
• Livor Mortis: Blood pooling in the body, indicating if a body was moved.
• Algor Mortis: Body cooling after death, can be helpful with timing.
• Time of Death: Accurate estimations around 12 hours after death.
• Post-Mortem Shutdown: Respiratory, circulatory, central nervous systems cease in that order; cellular metabolism then ends.
• Decomposition Start: Begins internally.
• Stomach Content: Can provide clues about time of death according to digestion level
• Vitreous Potassium: Potassium in the eye fluid may be used as a time indicator after death.
• Autolysis: Body's digestive enzymes breaking down tissues
• Putrefaction: Bacteria and fungi breakdown proteins
• Estimating Time of Death: Environmental details (mail, newspaper, light, etc.), daily habits, and microbiomes help

Evidence in Court

• Evidence: Information used to make a fact more or less likely
• Trier of Fact: Jury or judge, who determines the relevant evidence's importance
• Real Evidence: Found at the crime scene
• Demonstrated Evidence: Added later to explain the crime scene or evidence already found.
• Locard Exchange Principle: Exchange of material when items or people are in contact.
• Evidence Transfer Conditions: Pressure, contact frequency, materials' characteristics affect transfer.
• Evidence Persistence: Transfer remains, persisting until it degrades, transfers again, or is collected
• Classification of Evidence: Identity (physical properties), class (subgroups), individualization (specific only, ex. unique fingerprint)
• Known & Questioned Evidence: Known—defined source; questioned—unknown source
• Controls (Positive & Negative): Positive—expected result; Negative—no result should occur; useful to rule out false positives or negatives.
• Type I & Type II Errors: Type I—false positive; Type II—false negative

Bloodstain Pattern Analysis

• Bloodstain Pattern Analysis (BPA): Provides forensic information about bloodshed events
• BPA Purpose: Determine actions and sequences leading to the bloodstains
• Bloodstain Types: Passive (gravity), spattered (force), altered (further modifications).